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Accipiter Behavior

posted by Jerry Liguori at
on Thursday, March 24, 2011 

One of the tips for identifying Cooper’s Hawk from Sharp-shinned Hawk is that Sharp-shinned Hawk may cock its tails up in certain conditions, whereas Cooper’s does not exhibit this behavior. Yes, it is true that almost every accipiter you see with its tail in this posture will be a Sharp-shined Hawk, but I have mentioned several times in the past “no field mark or behavior is 100% reliable”, and “a combination of traits makes an I.D.” Note in the photo above, both the juvenile Sharp-shinned (left) and juvenile Cooper’s (right) have the tail cocked upward. This is rare on Cooper’s, but it does happen.

There are several other traits normally associated with telling Cooper’s from Sharp-shinned that are not even close to 100% reliable. Some are not worth mentioning since they are often difficult or impossible to see in the field. However, the extent of the streaking on underbody, and the shape of the tail tip are worth mentioning. It is often said that the streaking to the underbody of juvenile Sharp-shinned is more prominent than that of Cooper’s, but this is not always true. There are many Cooper’s Hawks that are more heavily marked below than typical Sharp-shinneds. Also, the tail tip on Cooper’s is usually rounded compared to the square-tipped tail on Sharp-shinned. But, many Sharp-shinned Hawks (especially juvenile females) show rounded tail tips. Both of these features are shown in Hawks From Every Angle and Hawks at a Distance so I won’t clog the blog with multiple photos.

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